As this type of screw engagement type clamping apparatus, there is a conventional one described in Patent Document 1 (Japanese Unexamined Patent Publication No. 7-40165).
This conventional technique is constructed as follows.
A clamp rod is inserted vertically into a through hole of a base. The clamp rod is provided with a clamping external thread which engages with an internal threaded hole of an object to be fixed, an elevating external thread to be engaged with an elevating nut, and a pressing portion which presses the base from above, in the recited order toward the upward. Then, when an air impact wrench rotates the clamp rod, the clamp rod lowers according to screw engagement with the elevating nut, and the clamping external thread engages with the internal threaded hole of the object to be fixed. Thereby, the object is fixed to the base.    Patent Document 1: Japanese Unexamined Patent Publication No. 7-40165